It’s a football cliché that “teams are made in the image of their manager”. Although we would struggle to explain the actual mechanisms involved, we find it quite natural to imagine that the unit of 11 players has somehow become an extension of the man’s personality on the sideline who does the post-match interviews.

So when Manchester United score a late goal, we praise Alex Ferguson’s indomitable determination. When Liverpool pass the ball 600 times without scoring, we criticise Brendan Rodgers for talking too much.

For obvious reasons, it’s the managers with the strongest personalities whose teams are most often said to reflect their characters. Not everyone agrees Martin O’Neill is a brilliant manager, but few would deny he is one of the most distinctive personalities in the game.

It's a struggle to remember the goals in Celtic's 3-2 defeat at Juventus in September 2001, but I will never forget the fulminating interview O'Neill gave afterwards. Celtic had fought back from 2-0 down to equalise before losing to a late penalty that O'Neill considered unjust. He appeared before the cameras almost hyperventilating with indignation, voice rising, eyes ablaze.

“We were extraordinary!” exclaimed O’Neill, rolling his Rs superbly. “Extraordinary! It’s absolutely extraordinary. We were magnificent. Magnificent! Coming roaring in there against Juventus who’ve spent a hundred million pounds, we were fantastic! Players there, devastated in the dressingroom as I am myself. It’s shocking! Wave after wave after wave after wave of attack! We’ve got everybody forward! At 2-2 there’s only one winner! We’re going for it! And suddenly, I’ve turned away from the incident, I thought it was going for a goal kick, I cannot believe he’s pointed to the spot!”

Magnificent figure

Everyone watching immediately understood why Celtic had played so well. The team was the incarnation of the fire raging in the belly of this magnificent figure. O’Neill embodied the qualities of fervour and defiance that Celtic supporters prize most. With Celtic driven on by the irresistible energy of O’Neill, no wonder Juventus needed the referee to help them over the line.

O’Neill won three Scottish titles with Celtic and two League Cups with Leicester City. The lasting admiration he won with these trophies owed at least as much to his style as to his substance. What impressed people most about O’Neill was not tactics, coaching nor transfer market acumen – it was his personality.

Imagine O’Neill had come out after that Juventus match and declared that the reason Celtic had lost was that, compared to their opponents, they “lacked real, true ability”. Who could have argued? Juventus had stars like Buffon, Thuram, Davids, Salas and Del Piero. Celtic’s only player on that level was Henrik Larsson.

The O’Neill who managed Celtic would never have said such a thing. Last month he used those very words about his Sunderland team, a few days after they lost 3-1 to QPR. Sunderland lack ability, but in football there is a fine line between realism and defeatism. Managers are usually best advised not to pass withering judgments on their teams when there are so many others happy to do it for them.

If it was disappointing for Sunderland chairman Ellis Short to hear his manager speaking in such despondent terms, it was not entirely surprising. It had already been widely noted O'Neill seemed different from his former self. He had become reflective, at times almost introverted, no longer a human exclamation mark.

O’Neill teams always had a certain reputation: they scored when you didn’t expect it, defeated opponents they weren’t supposed to beat. He jumped up and down on the sideline and raged in interviews.

This season neither O’Neill nor his team measured up to that reputation. Just as he evolved towards a more subdued personal style, he found himself managing the first truly bad team of his career.

Prisoner of his past

It might be no more than an unfortunate coincidence, but the natural inclination is to see a connection. O’Neill is a prisoner of his past. When your reputation is built on showmanship, you’d better keep up the show.

Of course, all that is just a matter of perception. The real reason why O’Neill has been less successful since he left Celtic probably has less to do with the dimming of his inner fire than with his preference for working with players from Britain and Ireland. Of his last 25 signings at Sunderland and Villa, only three came from clubs outside Britain and all but five spoke English as a first language.

Buying British worked in the days when English football was insular and there was a limit on the number of foreign players you could sign. It doesn’t work any more. The first reason is that because clubs in Britain are relatively rich, it’s costly to buy their players. The second is that most of the best players are to be found outside Britain. Buying British is now an expensive way to end up with a mediocre squad. It happened at Villa under O’Neill and Short didn’t want it to happen again at his club.

O'Neill's apparent reluctance to adapt to that new reality, combined with his record of spending big money at Villa and Sunderland, might mean that Premier League chairmen will hesitate to offer him another job. International football looks like the logical next step.